Shellfish harvesters: know before you dig

Published on Wed, Aug 20, 2014 by Ian Ferguson

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Joshua Leinbach, an environmental health specialist with the Whatcom County Health Department (WCHD), knows why it’s critical that recreational shellfish harvesters are aware that a beach has been closed to harvesting. And, after the presentation he made at an August 6 meeting, so do members of the Blaine Chamber of Commerce.

Tom Kunesh, the food safety program supervisor for WCHD, compiled the presentation Leinbach gave to the Blaine Chamber of Commerce. 

All of Whatcom County has been closed to recreational shellfish harvesting since July 2 due to increased levels of diarrhetic shellfish poisoning (DSP), a marine biotoxin. The WCHD collects routine mussel samples every other week, and if biotoxins are detected in an area the sample collection increases from biweekly to weekly. Samples are sent to the Washington State Public Health Lab for analysis.

“It’s hard to pin down what exactly causes these toxin levels to swell so dramatically, which is why we test every week when we find elevated levels,” Leinbach said.

Marine biotoxins are naturally occurring in algae, but when the amount of algae in an area increases too much, the filter feeders that eat the algae accumulate the toxins, making them unsafe to eat. A variety of factors, from a large rain event to a long streak of sunny weather, can cause an algae bloom. The blooms usually occur during the summer months.

Crab meat is not affected by the biotoxins, Leinbach said, but the innards, or “butter,” of the crab is. If an area is closed to shellfish harvesting, people harvesting crabs from that area should refrain from eating the crab butter.

The effects of marine biotoxins vary, depending on the type of toxin. 

Diarrhetic shellfish poisoning causes diarrhea, vomiting and abdominal pain. It was first found in Washington five years ago, and there were two outbreaks in Washington and B.C. in 2011.

Paralytic shellfish poisoning, also known as “red tide,” causes numbness and tingling in the lips, tongue, fingers and toes in mild cases. It may also cause gastrointestinal symptoms. In severe cases, it can lead to paralysis and death.

Amnesic shellfish poisoning is rarely detected at harmful levels. In mild cases, it causes nausea, vomiting and diarrhea. In severe cases, it can lead to the permanent loss of short-term memory.

A hotline run by the Washington Department of Health tells users whether the area they want to dig for clams, mussels and other shellfish has been closed due to unsafe levels of marine biotoxin. The number is 800/562-5632.